1. Field of the Invention
The present invention relates to an array substrate for a liquid crystal display device, and a manufacturing method thereof.
2. Description of the Background Art
A liquid crystal display device includes an opposite substrate, a liquid crystal, and an array substrate. The liquid crystal is arranged between the opposite substrate and the array substrate, and display voltage is applied to the liquid crystal by the array substrate. The array substrate includes a plurality of gate lines and a plurality of source lines. The gate line and the source line intersect each other interposing an insulating layer therebetween. An alignment film is formed on the upper layer of the gate lines and the source lines, and this alignment film specifies the alignment state of the liquid crystal in a state where display voltage is not applied.
On the surface of the alignment film, a step that is dependent on the step of the layer below itself is formed, and a protruding section is formed at a part facing the source line, for example. Also, a rubbing process is performed on the alignment film at the time of manufacture. This rubbing process is performed by rubbing the surface of the alignment film with a cloth while a rubbing roller having this cloth attached to its surface is rolling.
A liquid crystal display device of a transverse electric field method, such as an In Plane Switching method or an FFS (Fringe Field Switching) method, for driving a liquid crystal by generating a transverse electric field substantially parallel to a substrate in the liquid crystal, sometimes adopts so-called multi-domain pixels. Such a multi-domain pixel has a bent shape, for example. More specifically, each pixel has a shape where two parallelograms are joined in a line-symmetric manner with respect to one side of the parallelogram, for example. According to such a multi-domain pixel, two domains divided by this one side have the liquid crystals aligned in different directions to each other. The viewing angle may thereby be widened.
Also, since a pair of sides of each pixel is bent, the source line along the sides also extends while being bent (that is, in a meandering manner).
Now, as described above, a protruding section caused by the source line is formed on the surface of the alignment film. Accordingly, this protruding section also extends while being bent according to the pattern of the source line. When performing the rubbing process on such an alignment film, the inclined end face, of inclined end faces forming the protruding section of the alignment film, on the downstream side in the rubbing direction does not easily come in contact with the rubbing roller. This will be described in detail with respect to an embodiment.
When the rubbing process is insufficient on this inclined end face, the alignment state of the liquid crystal corresponding to the inclined end face is not made a desirable alignment state. This leads to reduction in the display performance (light leakage, reduced contrast, and the like).
To solve this problem, according to Japanese Patent Application Laid-Open No. 2012-113125, a light-shielding layer (black matrix) having an enough width for covering the protruding section of the alignment film is provided. Then, even if there is a region in the protruding section of the alignment film where the rubbing process is insufficient, the light passing through the region is blocked by the light-shielding layer. Accordingly, reduction in the display performance that is caused by alignment abnormality may be prevented. However, an increase in the width of the light-shielding layer leads to reduction in the aperture ratio and sacrifices the luminance characteristic.